Sealed Body, Method for Manufacturing Sealed Body, Light-Emitting Device, and Method for Manufacturing Light-Emitting Device

ABSTRACT

A highly productive method for sealing substrates with the use of glass frit is provided. A method for sealing substrates with the use of glass frit, which can be used for a substrate provided with a material having low heat resistance, is provided. A highly airtight sealed body which is manufactured by such a method is provided. A light-emitting device having high productivity and high reliability and a manufacturing method thereof are provided. A heat generation layer containing a conductive material which generates heat by induction heating is formed to overlap with a region where a paste including a frit material and a binder is applied. Alternatively, a conductive material which generates heat by induction heating is added to the paste itself. The paste is locally heated by induction heating to remove the binder included in the paste.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a sealed body including two substratesand a method for manufacturing the sealed body. Further, the presentinvention relates to a light-emitting device including an organic ELelement and a method for manufacturing the light-emitting device.

2. Description of the Related Art

A technique in which a highly airtight sealed body is formed in such amanner that two substrates are bonded to each other by glass frit (alsoreferred to as frit glass) including low-melting glass is known. In atechnique disclosed in Patent Document 1, a paste containing a binderand a frit material including low-melting glass is applied to a glasssubstrate along an edge of the glass substrate, the binder is removedand the frit material is melted to form glass frit by baking of thepaste, the glass frit is irradiated with laser light with the substrateoverlapping with a counter substrate, and the glass frit is melted sothat the substrate and the counter substrate are bonded to each other bythe glass frit; thus, a highly airtight sealed body is formed.

Since glass frit has a high gas barrier property, a space sealed withthe glass frit can be kept away from the external atmosphere. A methodfor sealing with such glass frit is used for a device including anelement, such as an organic EL element, whose performance is rapidlydecreased once the element is exposed to air (including moisture,oxygen, or the like).

As examples of the device including the organic EL element, a lightingdevice, an image display device in which a thin film transistor and anorganic EL element are combined, and the like can be given. Since theorganic EL element can be formed into a film and a large-area organic ELelement can be easily formed, a lighting device including a planar lightsource can be provided using the organic EL element. Further, since abacklight is not needed for an image display device including theorganic EL element, the image display device can be thin and lightweight, and have high contrast.

REFERENCE Patent Document

[Patent Document 1] Japanese Published Patent Application No. 2011-65895

SUMMARY OF THE INVENTION

As described above, in the method for sealing with the glass frit, thepaste including the frit material and the binder needs to be baked forremoving the binder after the paste is applied to the substrate. Thebinder is removed, so that the glass frit after being irradiated withlaser light can have a high gas barrier property. Although bakingtemperature depends on the material, baking at a high temperature ofapproximately 350° C. to 450° C. generally needs to be performed forremoving the binder completely.

In general, a heating apparatus such as an oven or an annealing furnaceis used for baking a paste. However, such a heating apparatus is largein size and it takes a long time to reach desired baking temperature dueto heat capacity of a substrate. Accordingly, productivity is greatlyaffected by a long process time in a step of baking the paste, highinitial cost and running cost of the heating apparatus, and the like.

A substrate to which a paste is applied cannot be baked at hightemperature in some cases. For example, in the case where an organicsubstance with low heat resistance is formed over a substrate, heattreatment at high temperature cannot be performed on the substrate aftera paste is applied to the substrate. In the case of an organic ELdevice, a color filter, an optical adjustment layer for improving lightextraction efficiency, such as a micro lens array, and the like can begiven as examples of an element with low heat resistance formed over asubstrate.

The present invention is made in view of the foregoing technicalbackground. Therefore, an object of an embodiment of the presentinvention is to provide a highly productive method for sealingsubstrates with glass frit. Further, an object is to provide a methodfor sealing substrates with glass frit, which can also be used for asubstrate for which a material with low heat resistance is provided.Further, an object is to provide a highly airtight sealed body which ismanufactured by either of the above methods. Further, an object is toprovide a light-emitting device with high productivity and highreliability and a method for manufacturing the light-emitting device.

An embodiment of the present invention achieves at least one of theabove objects.

In order to achieve the above objects, the present invention focuses onbaking by locally heating a region to which a paste including a fritmaterial and a binder is applied after the paste is applied to asubstrate. A heat generation layer containing a conductive materialwhich generates heat by induction heating is formed to overlap with theregion to which the paste is applied. Alternatively, a conductivematerial which generates heat by induction heating is added to the pasteitself. By the above methods, the region to which the paste is appliedor the paste itself can be locally heated.

An induction heating method is a method by which an object to be heatedis heated in a non-contacting manner utilizing an electromagneticinduction phenomenon. For example, when a conductive object to be heatedis located within a magnetic field created by a coil connected to analternating-current power source, eddy current is generated within theobject to be heated due to change in the magnetic field created by thecoil, and the object to be heated itself can be heated by Joule heat ofthe current without any contact.

By such an induction heating method, a conductive object to be heateditself can be heated. Therefore, with the use of the induction heatingmethod, heat treatment can be performed quickly regardless of heatcapacity of a substrate to which a paste is applied; thus, time forperforming baking treatment can be greatly reduced. Further, sinceinduction heating can be performed with a device having a simplestructure, the structure of the device used in the induction heating canbe simpler than that used in a heating method using an oven or anannealing furnace, and productivity can be increased.

Further, the paste is locally baked by such an induction heating method,so that a region where the paste is not provided is hardly affected.Accordingly, even in the case where a material with low heat resistanceis provided over a substrate, a paste can be baked without thermaleffect on such a material.

In other words, an embodiment of the present invention is a method formanufacturing a sealed body, including the steps of forming a heatgeneration layer over a first substrate; forming a frit paste includinga frit material and a binder over the heat generation layer; heating theheat generation layer by induction heating to remove the binder and tofuse the frit material so that glass frit is formed; arranging the firstsubstrate and a second substrate so that the first substrate and thesecond substrate face each other and that the glass frit and the secondsubstrate are closely attached to each other; and irradiating the glassfrit with laser light to bond the glass fit to the second substrate, sothat a closed space surrounded by the first substrate, the secondsubstrate, the glass fit, and the heat generation layer is formed. Thefrit paste has a shape of a closed curve.

An embodiment of the present invention is a method for manufacturing asealed body, including the steps of forming a frit paste including afrit material, a binder, and a conductive material over a firstsubstrate; heating the frit paste by induction heating to remove thebinder and to fuse the fit material so that glass frit is formed;arranging the first substrate and a second substrate so that the firstsubstrate and the second substrate face each other and that the glassfrit and the second substrate are closely attached to each other; andirradiating the glass frit with laser light to bond the glass frit tothe second substrate, so that a closed space surrounded by the firstsubstrate, the second substrate, and the glass frit is formed. The fritpaste has a shape of a closed curve.

In the above method, a paste including a material generating heat byinduction heating is used, whereby a step, of forming a heat generationlayer can be omitted, resulting in improvement of productivity.

Further, an embodiment of the present invention is a sealed bodyincluding a first substrate, a second substrate, and glass fritincluding a conductive material. A closed space surrounded by the firstsubstrate, the second substrate, and the glass frit is formed.

When a sealed body is formed by either of the above manufacturingmethods, the sealed body can have high productivity and highairtightness.

Further, an embodiment of the present invention is a method formanufacturing a light-emitting device, including the steps of forming aheat generation layer over a surface of a first substrate; forming afrit paste including a frit material and a binder over the heatgeneration layer; heating the heat generation layer by induction heatingto remove the binder and to fuse the frit material so that glass frit isformed; forming a light-emitting unit including an EL element over asurface of a second substrate; arranging the first substrate and thesecond substrate so that the first substrate and the second substrateface each other and that the glass frit and the second substrate areclosely attached to each other; and irradiating the glass frit withlaser light to bond the glass frit to the second substrate, so that aclosed space which is surrounded, by the first substrate, the secondsubstrate, the glass frit, and the heat generation layer and in whichthe light-emitting unit is enclosed is formed. The frit paste has ashape of a closed curve.

Further, an embodiment of the present invention is a method formanufacturing a light-emitting device, including the steps of forming afrit paste including a frit material, a binder, and a conductivematerial over a surface of a first substrate; heating the frit paste byinduction heating to remove the binder and to fuse the frit material sothat glass frit is formed; forming a light-emitting unit including an ELelement over a surface of a second substrate; arranging the firstsubstrate and the second substrate so that the first substrate and thesecond substrate face each other and that the glass frit and the secondsubstrate are closely attached to each other; and irradiating the glassfrit with laser light to bond the glass fit to the second substrate, sothat a closed space which is surrounded by the first substrate, thesecond substrate, and the glass frit and in which the light-emittingunit is enclosed is formed. The frit paste has a shape of a closedcurve.

An embodiment of the present invention is a light-emitting deviceincluding a first substrate, a second substrate provided with alight-emitting unit, and glass frit including a conductive material. Aclosed space which is surrounded by the first substrate, the secondsubstrate, and the glass frit and in which the light-emitting unit isenclosed is formed.

As described above, the sealed body and the method for manufacturing thesealed body according to embodiments of the present invention can beused for a light-emitting device including a light-emitting unit. Thus,a light-emitting device with high productivity and high reliability canbe manufactured.

Further, an embodiment of the present invention is a method formanufacturing a light-emitting device, including the steps of forming aheat generation layer over a surface of a first substrate; forming acolor filter in a region which does not overlap with the heat generationlayer over the surface of the first substrate; forming a frit pasteincluding a frit material and a binder over the heat generation layer;heating the heat generation layer by induction heating to remove thebinder and to fuse the frit material so that glass frit is formed;forming a light-emitting unit including an EL element over a surface ofa second substrate; arranging the first substrate and the secondsubstrate so that the color filter and the light-emitting unit face eachother and that the glass frit and the second substrate are closelyattached to each other; and irradiating the glass frit with laser lightto bond the glass frit to the second substrate, so that a closed spacewhich is surrounded by the first substrate, the second substrate, theglass frit, and the heat generation layer and in which thelight-emitting unit and the color filter are enclosed is formed. Thefrit paste has a shape of a closed curve and surrounds the color filter.

Further, an embodiment of the present invention is a method formanufacturing a light-emitting device, including the steps of forming acolor filter over a surface of a first substrate; forming a frit pasteincluding a frit material, a binder, and a conductive material over thesurface of the first substrate; heating the frit paste by inductionheating to remove the binder and to fuse the frit material so that glassfrit is formed; forming a light-emitting unit including an EL elementover a surface of a second substrate; arranging the first substrate andthe second substrate so that the color filter and the light-emittingunit face each other and that the glass frit and the second substrateare closely attached to each other; and irradiating the glass frit withlaser light to bond the glass frit to the second substrate, so that aclosed space which is surrounded by the first substrate, the secondsubstrate, and the glass frit and in which the light-emitting unit andthe color filter are enclosed is formed. The frit paste has a shape of aclosed curve and surrounds the color filter.

In an embodiment of the present invention, particularly in the casewhere a sealing method using glass frit is used for a top-emissiondisplay device including a color filter, the paste needs to be appliedto either a substrate for which an organic EL element is provided or acounter substrate for which a color filter is provided and to be baked.However, since the organic EL element and the color filter have low heatresistance, baking cannot be performed.

Alternatively, a color filter may be formed after baking of the paste.In the case of a high-definition display device, the color filter isgenerally formed by a photolithography method; therefore, the colorfilter might not be evenly formed at an end portion of the glass frit inthe step of forming a film of the color filter.

Therefore, with the use of a method for baking a paste by inductionheating according to an embodiment of the present invention, a highlyreliable display device including a color filter can be manufactured.

An embodiment of the present invention is a light-emitting deviceincluding a first substrate provided with a color filter; a secondsubstrate provided with a light-emitting unit; and glass frit includinga conductive material. A closed space which is surrounded by the firstsubstrate, the second substrate, and the glass frit and in which thecolor filter and the light-emitting unit facing each other are enclosedis formed.

By any of the above methods, a highly reliable light-emitting device canbe manufactured. Further, a highly reliable light-emitting deviceincluding a color filter can be manufactured.

Note that a “closed curve” in this specification and the like means acontinuous curve with no endpoints. Further, here, a “curve” includesconcepts of a straight line and a line segment in its broad sense.Therefore, the case where a plurality of line segments is included andevery end point of the line segments overlaps with another end point,such as a periphery of a quadrangle, is also one mode of the closedcurve. Further, a polygon, a circle, an ellipse, a shape in which aplurality of curves having different curvatures is continuouslyconnected, a shape including a straight line and a curve, or the like isalso one mode of the closed curve.

Note that in this specification and the like, the term EL layer refersto a layer provided between a pair of electrodes of a light-emittingelement and including at least a layer including a light-emittingorganic compound (also referred to as a light-emitting layer), or astack including the light-emitting layer.

Note that a light-emitting device in this specification refers to adevice including an image display device, a light-emitting unit, or alight source. Therefore, a display device including an image displaydevice, a lighting device including a light-emitting unit or a lightsource, or the like is an embodiment of the light-emitting device. Inaddition, the light-emitting device includes any of the followingmodules in its category: a module in which a connector such as aflexible printed circuit (FPC), a tape automated bonding (TAB) tape, ora tape carrier package (TCP) is attached to a light-emitting device; amodule having a TAB tape or a TCP provided with a printed wiring boardat the end thereof; and a module having an integrated circuit (IC)directly mounted over a substrate over which a light-emitting element isformed by a chip on glass (COG) method.

According to an embodiment of the present invention, a highly productivemethod for sealing substrates with glass frit can be provided. Further,a method for sealing substrates with glass frit, which can be used for asubstrate provided with a material with low heat resistance, can beprovided. Further, a highly airtight sealed body manufactured in eithermethod can be provided. A light-emitting device with high productivityand high reliability and a manufacturing method thereof can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIGS. 1A to 1D illustrate a method for manufacturing a sealed body,according to an embodiment of the present invention;

FIGS. 2A and 2B illustrate a method for manufacturing a sealed body,according to an embodiment of the present invention;

FIGS. 3A to 3E illustrate a method for manufacturing a sealed body,according to an embodiment of the present invention;

FIGS. 4A to 4D illustrate a method for manufacturing a light-emittingdevice, according to an embodiment of the present invention;

FIGS. 5A and 5B illustrate a light-emitting device according to anembodiment of the present invention;

FIGS. 6A and 6B illustrate a light-emitting device according to anembodiment of the present invention;

FIGS. 7A to 7C each illustrate an EL layer according to an embodiment ofthe present invention; and

FIGS. 8A to 8E illustrate electronic devices according to embodiments ofthe present invention.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments will be described in detail with reference to the drawings.Note that the present invention is not limited to the followingdescription, and it will be easily understood by those skilled in theart that various changes and modifications can be made without departingfrom the spirit and scope of the present invention. Therefore, thepresent invention should not be construed as being limited to thedescription in the following embodiments. Note that in the structures ofthe invention described below, the same portions or portions havingsimilar functions are denoted by the same reference numerals indifferent drawings, and description of such portions is not repeated.

Note that in each drawing referred to in this specification, the size,the layer thickness, or the region of each component is exaggerated forclarity in some cases. Therefore, embodiments of the present inventionare not limited to such scales.

Embodiment 1

In this embodiment, a method for manufacturing a sealed body, accordingto an embodiment of the present invention, will be described withreference to FIGS. 1A to 1D, FIGS. 2A and 2B, and FIGS. 3A to 3E.

<Manufacturing Method Example 1>

FIGS. 1A to 1D and FIGS. 2A and 2B illustrate a method for manufacturinga sealed body described in this manufacturing method example. In each ofFIGS. 1A to 1D and FIGS. 2A and 2B, a schematic top view and acorresponding schematic cross-sectional view are illustrated.

First, a heat generation layer 113 is formed over a first substrate 111(see FIG. 1A). The heat generation layer 113 includes a conductivematerial which can generate heat in later induction heating treatment.The heat generation layer 113 includes a material which generates heatenough to heat a frit paste 115 formed over the heat generation layer113 so that a binder in the frit paste 115 is removed and a fritmaterial in the frit paste 115 is melted. Note that a material which canwithstand at least temperature at which the binder contained in the fritpaste 115 is removed is used for the heat generation layer 113.

As a material which can generate heat by induction heating, at least aconductive material can be given. For example, a metal material can beused. It is preferable to use a conductive material having relativelyhigh resistance because heat can be efficiently generated by inductionheating. For example, iron, tungsten, molybdenum, stainless steel, analloy containing any of them, or the like can be given. The heatgeneration layer 113 may be a stack including films including the abovematerials.

As described later, in an induction heating method, a portion closer toa surface of a conductor generates a larger amount of heat, andtransmission of electromagnetic waves inside the conductor depends onfrequency used, physical properties of the conductor (e.g., electricconductivity and magnetic permeability), or the like. Therefore, thethickness of the heat generation layer 113 is set as appropriate inaccordance with the material of the heat generation layer 113 and thefrequency used in induction heating performed later. The thickness ofthe heat generation layer 113 is preferably greater than or equal to 0.5μm and less than or equal to 100 μm.

The heat generation layer 113 can be formed in such a manner that aconductive film is formed over the first substrate 111 by a depositionmethod such as a sputtering method or a CVD method and then anunnecessary region of the conductive film is removed by a patterningtechnique such as a photolithography method. However, the method forforming the heat generation layer 113 is not limited thereto. The heatgeneration layer 113 may be formed by a plating method, a printingmethod such as a screen printing method, or a discharging method such asan inkjet method. The heat generation layer 113 is preferably formed tohave a shape of a closed curve, which is approximately the same patternas the pattern of the frit paste 115 formed later, along an outerperiphery of the first substrate 111. The heat generation layer 113 isnot necessarily formed to have a shape of a closed curve, and mayinclude one or more of island-shaped patterns to be overlapped by thefrit paste 115 formed later.

Next, the frit paste 115 is formed over the heat generation layer 113(see FIG. 1B). The frit paste 115 includes the frit material formed ofpowder glass and the binder, and can be formed by a printing method suchas a screen printing method, a dispensing method, or the like. The fritpaste 115 is formed to have a shape of a closed curve along the outerperiphery of the first substrate 111.

It is preferable that the frit material include one or more compoundsselected from a group of, for example, magnesium oxide, calcium oxide,barium oxide, lithium oxide, sodium oxide, potassium oxide, boron oxide,vanadium oxide, zinc oxide, tellurium oxide, aluminum oxide, silicondioxide, lead oxide, tin oxide, phosphorus oxide, ruthenium oxide,rhodium oxide, iron oxide, copper oxide, titanium oxide, tungsten oxide,bismuth oxide, antimony oxide, lead borate glass, tin phosphate glass,vanadate glass, and borosilicate glass. For example, a binder formedusing a resin diluted with an organic solvent is mixed with the fritmaterial; thus, the frit paste is formed.

A buffer layer for improving adhesion between the heat generation layer113 and glass frit 119 formed later may be formed between the heatgeneration layer 113 and the frit paste 115. The buffer layer can beformed using an insulator having high heat resistance, such as an oxideor a nitride. For example, a silicon oxide film, a silicon nitride film,an aluminum oxide film, or the like can be used.

Next, the heat generation layer 113 is made to generate heat byinduction heating using an induction heating apparatus 131; thus, thefrit paste 115 over the heat generation layer 113 is baked (see FIG.1C).

The induction heating apparatus 131 includes a coil 133 and analternating-current power supply is connected to the coil 133. An outputcontrol circuit (not illustrated) is provided for the induction heatingapparatus 131. The output control circuit controls alternating-currentflowing through the coil 133 to control the frequency and the intensityof a magnetic field created by the coil 133 in the induction heatingapparatus 131. The coil 133 is arranged in accordance with a position ofthe heat generation layer 113 so that the heat generation layer 113which is an object to be heated uniformly generates heat.

Eddy current is generated in the heat generation layer 113 within themagnetic field created by the coil 133 in the induction heatingapparatus 131, and the heat generation layer 113 generates heat usingJoule heat of the eddy current. Thus, the frit paste 115 formed over theheat generation layer 113 can be heated by the heat generated by theheat generation layer 113.

The binder in the frit paste 115 is removed by this heating. Further, inthis heating, the powder glass included in the frit material in the fritpaste 115 is melted, fused, and then solidified; thus, glass frit 117 isformed.

It is known that in an induction heating method, a portion closer to asurface of a conductor generates a large amount of heat and heatgeneration decreases exponentially as the distance from the surfaceincreases. As the lower frequency is used, a portion deeper inside theconductor can be heated. In this structure example, only the frit pasteover the heat generation layer 113 needs to be heated; therefore,frequency is selected in accordance with the material and the thicknessof the heat generation layer 113 so that at least a surface of the heatgeneration layer 113 sufficiently generates heat. Further, higherfrequency is preferable because heating time can be shortened. Thefrequency in the range of higher than or equal to 1 Hz and lower than orequal to 10 MHz, preferably higher than or equal to 1 kHz and lower thanor equal to 5 MHz is used.

Thus, by an induction heating method, it is possible to heat the heatgeneration layer 113 quickly, so that the frit paste 115 can be baked inan extremely short time, resulting in an increase in productivity.

Next, a sealant 121 fainted. The sealant 121 is provided for temporarilybonding the first substrate to the second substrate. The first substrateand the second substrate are temporarily bonded to each other by thesealant 121, whereby a position of the first substrate relative to thesecond substrate is not changed. Note that in the case where the firstsubstrate and the second substrate are not necessarily strictly aligned,the sealant 121 is not necessarily formed.

The sealant 121 is preferably positioned outside the glass frit 117.Although the sealant 121 may be formed inside the glass frit 117 havinga shape of a closed curve, when the sealant 121 is formed outside theglass frit 117, an impurity such as an organic solvent included in thesealant 121 can be prevented from remaining in a sealed region inattachment of the substrates. This is preferable because the sealedregion can be made clean. Further, the sealant 121 is preferably formedto have a shape of a closed curve similar to the glass frit 117. Thesealant 121 is formed to have a shape of a closed curve so as tosurround the glass frit 117, whereby a laser irradiation step performedlater can be performed in the air. Accordingly, an apparatus used in thelaser irradiation step can have a simple structure.

The sealant 121 can be formed by a printing method such as a screenprinting method, or a dispensing method, for example. The sealant 121 isformed thicker than at least a stack of the glass frit 117 and the heatgeneration layer 113. A photocurable resin, preferably an ultravioletcurable region can be used for the sealant 121.

Then, the second substrate 101 and the first substrate 111 over whichthe glass frit 117 and the sealant 121 are formed are bonded to eachother (see FIG. 2A).

The first substrate 111 and the second substrate 101 are bonded to eachother so that the sealant 121 is closely attached to the secondsubstrate 101. After that, the sealant 121 is irradiated withultraviolet light 135 to be cured, so that the first substrate 111 andthe second substrate 101 are temporality bonded to each other. Thesealant 121 is cured and becomes a sealant 123 when irradiated with theultraviolet light 135.

The bonding step is preferably performed in an atmosphere which does notinclude water, oxygen, or the like, for example, in an atmosphere of aninert gas such as a rare gas or nitrogen, or in a reduced-pressureatmosphere. When the bonding step is performed in such an atmosphere;the sealed region can be filled with a clean atmosphere.

Irradiation of the ultraviolet light 135 is performed in such a mannerthat, for example, as illustrated in FIG. 2A, a shielding plate 137which does not transmit ultraviolet light is attached to a side which isirradiated with the ultraviolet light 135 and irradiation of anultraviolet ray is performed using an ultraviolet lamp or the like. Atthis time, it is preferable that the sealed region be shielded from theultraviolet light 135 by the shielding plate 137 and that pressure beapplied from the outside. With the application of the pressure from theoutside, the glass frit 117 is bonded to the second substrate 101 andthus temporary bonding can be performed. Note that the method ofirradiation of the ultraviolet light 135 is not limited thereto.Irradiation of the ultraviolet light 135 may be performed along thesealant 121 with the use of a linear light source, or irradiation of theultraviolet light 135 may be performed while the first substrate 111 isrelatively scanned with a light source. By any of the irradiationmethods, the shielding plate 137 is preferably provided for preventingdiffusion of ultraviolet light inside the sealed region.

In this manufacturing method example, the irradiation of the ultravioletlight 135 is performed from the first substrate 111 side; however, theirradiation of the ultraviolet light 135 may be performed from thesecond substrate 101 side in a similar manner.

Next, the glass frit 117 is irradiated with laser light 141, so that thefirst substrate 111 and the second substrate 101 are bonded to eachother (see FIG. 2B).

Irradiation of the laser light 141 is performed while a region where theglass frit 117 is formed is scanned with the laser light 141. The stepof irradiation of the laser light 141 is preferably performed while thepressure is applied from the outside to the first substrate 111 and thesecond substrate 101. The glass frit 117 is melted by the laser light141 to be bonded to the second substrate 101 in their contact portion.After that, the glass frit 117 is solidified, so that glass frit 119which bonds the heat generation layer 113 to the second substrate 101 isformed. Since the glass frit 119 has an extremely high gas barrierproperty, a closed area (also referred to as a sealed region) which issurrounded by the first substrate 111, the second substrate 101, and theglass frit 119 is completely shielded from the external air.

The irradiation of the laser light 141 can be performed from alight-transmitting substrate side. The irradiation of the laser light141 may be performed from either the first substrate 111 side, which isprovided with the heat generation layer 113, or the second substrate 101side. In the case where the heat generation layer 113 has a lightabsorption property with respect to the laser light 141 having apredetermined wavelength, the heat generation layer 113 is heated andthe glass frit 117 can be indirectly heated; thus, the glass frit 117can be heated more efficiently.

As the laser light 141, laser light having a wavelength which allows thelaser light to transmit a substrate on the side irradiated with thelaser light and energy which is large enough to heat one of or both theglass frit 117 and the heat generation layer 113 is used. As the laserlight 141, an Nd:YAG laser, a semiconductor layer, or the like ispreferably used, for example. Note that an absorber which absorbs lighthaving the wavelength of the laser light 141 may be added to the glassfrit 117.

In the case where the sealant 123 is formed outside the glass frit 117to have a shape of a closed curve, the step of the irradiation of thelaser light 141 can be performed in the air. In other words, since thesealed region is shielded from the external air by the sealant 123, animpurity such as water or oxygen included in the air can be preventedfrom entering the sealed region even when the step of the irradiation ofthe laser light 141 is performed in the air. Accordingly, an apparatusused for the irradiation of the laser light 141 can have a simplestructure. In the case where the sealant 123 is not provided or thesealant 123 has an island shape, the step of the irradiation of thelaser light 141 is preferably performed in a reduced-pressure atmosphereor an inert atmosphere.

In the case where the first substrate 111 and the second substrate 101are bonded to each other and the sealant 121 is irradiated with theultraviolet light 135 in a reduced-pressure atmosphere, the pressure inthe sealed region is kept reduced. Therefore, since atmospheric pressureis kept being applied to the first substrate 111 and the secondsubstrate 101 under the atmospheric pressure, the step of theirradiation of the laser light 141 can be performed without providing apressure application unit.

Through the above steps, a highly airtight sealed body 100 can bemanufactured.

A sealed body sealed by two substrates and glass fit is manufactured inthe above-described manner, so that the sealed body can have extremelyhigh airtightness. Further, when a frit paste is baked by inductionheating, the frit paste can be locally baked without directly heating asubstrate provided with the frit paste. Therefore, this method can alsobe used for a substrate provided with a material having low heatresistance. Furthermore, by an induction heating method, baking can beperformed in an extremely short time and a structure of an apparatusused for the baking can be simpler than that of an oven or a furnace.Accordingly, manufacturing cost and initial investment are suppressedand a highly productive method for manufacturing a sealed body can beprovided.

<Manufacturing Method Example 2>

When a conductive material is included in a frit paste, the frit pasteitself can be baked by an induction heating method without the heatgeneration layer 113. A method for manufacturing a sealed body with theuse of a frit paste including a conductive material will be describedbelow with reference to FIGS. 3A to 3E. Note that description of theportions described in Manufacturing Method Example 1 is omitted or issimply given.

FIGS. 3A to 3E illustrate a method for manufacturing a sealed bodydescribed in this manufacturing method example. Note that each of FIGS.3A to 3E illustrates a schematic cross-sectional view of a step.

First, a frit paste 155 is formed over the first substrate 111 (see FIG.3A).

The frit paste 115 to which a conductive material is added is used asthe frit paste 155. Any of the materials which can be used for the heatgeneration layer 113 can be used as the conductive material. Theconductive material is preferably a powder material and is mixed in thebinder together with the frit material. The diameter of the powdermaterial is larger than or equal to 1 nm and smaller than or equal to100 μm, preferably larger than or equal to 1 nm and smaller than orequal to 10 μm.

The frit paste 155 can be formed over the first substrate 111 in amanner similar to that described in Manufacturing Method Example 1.

Then, the frit paste 155 is heated using the induction heating apparatus131 (see FIG. 3B).

The conductive material in the frit paste 155 generates heat due to amagnetic field created by the coil 133 in the induction heatingapparatus 131, whereby the binder in the frit paste 155 is removed bythe generated heat and the powder glass in the frit material is melted.Thus, glass frit 157 is formed.

Next, in a manner similar to that described in Manufacturing MethodExample 1, the sealant 121 is formed (see FIG. 3C). Further, the firstsubstrate 111 over which the glass frit 157 is formed and the secondsubstrate 101 are attached to each other and irradiation of theultraviolet light 135 is perforated; thus, the first substrate 111 andthe second substrate 101 are temporarily bonded to each other (see FIG.3D).

After that, a region where the glass frit 157 is formed is selectivelyirradiated with the laser light 141. The glass frit 157 is melted by theirradiation of the laser light 141 and then solidified, so that glassfrit 159 which bonds the first substrate 111 to the second substrate 101is formed. It is preferable that the conductive material included in theglass frit 157 have an absorption property with respect to the laserlight 141 because the glass frit 157 can be heated more efficiently.Note that an absorber which absorbs light having the wavelength of thelaser light 141 may be added to the glass frit 157.

Through the above steps, a highly airtight sealed body 150 can bemanufactured.

Note that the glass frit 159 which has been subjected to the irradiationof the laser light 141 includes the conductive material. Particles ofthe powder conductive material are dispersed in the glass frit 159. Notethat the particles of the conductive material may partly gather in somecases.

With such a method, the step of forming the heat generation layer 113can be omitted, and a more highly productive method for manufacturing asealed body 150 can be provided. Further, the heat generation layer 113is not provided between the glass frit 159 and the first substrate 111,so that adhesion between the glass frit 159 and the first substrate 111is increased in some cases. For example, particularly in the case wherea glass substrate is used as the first substrate 111, adhesion betweenthe first substrate 111 and the glass frit 159 can be increased.

This embodiment can be combined with any of the other embodimentsdisclosed in this specification as appropriate.

Embodiment 2

In this embodiment, the method for manufacturing a sealed body accordingto an embodiment of the present invention, which is described inEmbodiment 1 as an example, is used for a light-emitting device. In thisembodiment, a method for manufacturing a light-emitting device includinga material having low heat resistance, particularly a light-emittingdevice including a color filter, will be described with reference toFIGS. 4A to 4D.

Note that in this embodiment, description of the portions described inEmbodiment 1 is omitted or is simply given.

<Manufacturing Method Example>

FIGS. 4A to 4D illustrate a method for manufacturing a light-emittingdevice described in this manufacturing method example. In each of FIGS.4A to 4D, a schematic top view and a corresponding schematiccross-sectional view are illustrated.

First, the heat generation layer 113 is formed over the first substrate111. The heat generation layer 113 can be formed using the material andthe method which are described in Embodiment 1.

Then, a color filter 181 is formed over the first substrate 111. Thecolor filter 181 is provided for adjusting a color of light emitted froma light-emitting unit 183 described later. In the case of a full-colorlight-emitting device (an image display device or a lighting devicecapable of adjusting a color), color filters having different colors areprovided. In that case, three colors, red (R), green (G), and blue (B),may be used, or four colors, red (R), green (G), blue (B), and yellow(Y), may be used. Further, a black matrix (BM) may be provided betweenthe color filters. In the case of a lighting device capable of adjustinga color, a color filter of one color may be provided, or a plurality ofcolor filters of two or more colors may be alternately provided instripes or in a tiled pattern. Further, a BM may be provided between thecolor filters. The color filter is provided to overlap with a pixel or aunit region of light emission in the light-emitting unit.

The color filter 181 can be formed in a desired position by a printingmethod, an inkjet method, a photolithography method, or the like. Inparticular, in a high-definition image display device, the color filter181 is preferably formed by a photolithography method.

An organic resin including a pigment can be used for the color filter181. Further, it is preferable that a light-transmitting chromatic resinbe used. A photosensitive or non-photosensitive organic resin can beused as such an organic resin. In the case where the color filter 181 isformed by a photolithography method, a photosensitive organic resin ispreferably used because a process can be simplified.

An overcoat layer covering the color filter 181 may be provided. Withthe overcoat layer, deterioration of the color filter 181 or leakage ofthe pigment from the color filter 181 can be suppressed; thus, a highlyreliable light-emitting device can be manufactured. The overcoat layercan be formed using a light-transmitting layer including an organicmaterial, a light-transmitting layer including an inorganic material, ora stack thereof.

Next, the frit paste 115 is formed over the heat generation layer 113.The frit paste 115 can be formed using the method described inEmbodiment 1.

FIG. 4A illustrates a schematic top view and a schematic cross-sectionalview at this stage.

Next, the heat generation layer 113 is heated by an induction heatingmethod with the use of the induction heating apparatus 131, so that thefrit paste 115 is indirectly baked (see FIG. 4B). The frit paste 115 isbaked, whereby the binder in the frit paste 115 is removed and the fritmaterial is melted, fused, and then solidified; thus, the glass frit 117is formed.

When an induction heating method is used in baking of the frit paste115, the heat generation layer 113 can be heated locally and the colorfilter 181 formed over the same substrate as the heat generation layer113 is hardly heated. Accordingly, the frit paste 115 can be bakedwithout a thermal effect on the color filter 181.

Further, by the induction heating method, it is possible to heat theheat generation layer 113 quickly, so that the frit paste 115 can bebaked in an extremely short time, resulting in an increase inproductivity. Moreover, even in the case where heat generated by theheat generation layer 113 is transmitted to the color filter 181 via thesubstrate, the adverse effect can be minimized because heating time isextremely short.

Next, the sealant 121 is formed over the first substrate 111. Thesealant 121 can be aimed using the method described in Embodiment 1.

Then, the first substrate 111 and the second substrate 101 which isprovided with the light-emitting unit 183 are attached to each other,and then the sealant 121 is irradiated with the ultraviolet light 135 tobe cured; thus, the second substrate 101 and the first substrate 111 aretemporarily bonded to each other (see FIG. 4C). By the irradiation ofthe ultraviolet light 135, the sealant 121 is cured and becomes thesealant 123 which bonds the first substrate 111 to the second substrate101.

The first substrate 111 and the second substrate 101 are attached toeach other so that a position of the light-emitting unit 183 relative tothe color filter 181 is not changed. Note that an alignment marker foralignment may be provided for the first substrate 111 and the secondsubstrate 101 in advance. In the case where the alignment marker isprovided for the first substrate 111, the alignment marker is preferablyformed at the same time as the heat generation layer 113 or the colorfilter 181 because the process can be simplified.

A light-emitting unit including an organic EL element can be used as thelight-emitting unit 183 provided for the second substrate 101. Forexample, a light-emitting unit having a large light-emitting portion,which is intended to be used as a lighting device, a passive matriximage display device, an active matrix image display device in which athin film transistor and an organic EL element are combined, or the likecan be used. An example of a structure which can be used for thelight-emitting unit 183 will be described in detail in Embodiment 3.

It is preferable that the organic EL element in the light-emitting unit183 provided for the second substrate 101 not be in contact with animpurity such as water or oxygen from the step of formation of thelight-emitting unit 183 to the end of the step of temporary bonding. Aseries of steps is preferably performed in an inert atmosphere or areduced-pressure atmosphere. In the case where the sealant 121 is formedto have a shape of a closed curve along the outer periphery of the firstsubstrate 111, a step after temporary bonding can be conducted in theair.

The glass frit 117 is irradiated with the laser light 141 to be meltedand then solidified; thus, the glass frit 119 which bonds the firstsubstrate 111 to the second substrate 101 is formed (see FIG. 4D). Theirradiation of the laser light 141 can be performed in a manner similarto the manner described in Embodiment 1.

Through the above steps, a light-emitting device 180 sealed with theglass frit 119 can be manufactured.

When the light-emitting device 180 is manufactured in such a manner, thelight-emitting device 180 can have high airtightness owing to the glassfrit 119; thus, a highly reliable light-emitting device in whichdeterioration of the enclosed light-emitting unit 183 due to an impuritysuch as water or oxygen is suppressed can be manufactured.

Sealing with glass frit can be used for a substrate provided with acolor filter having low heat resistance because a frit paste is baked byan induction heating method. Further, when the frit paste is baked by aninduction heating method, baking of the frit paste can be performed inan extremely short time and a structure of an apparatus used for thebaking can be simpler than that of an oven or a furnace. Accordingly,manufacturing cost and initial investment are suppressed and a highlyproductive method for manufacturing a sealed body can be provided.

This embodiment can be combined with any of the other embodimentsdisclosed in this specification as appropriate.

Embodiment 3

In this embodiment, an example of a structure of a light-emitting unitwhich can be used for the method for manufacturing a sealed bodyaccording to an embodiment of the present invention will be describedwith reference to FIGS. 5A and 5B and FIGS. 6A and 6B.

Structure Example 1

In this structure example, a passive matrix light-emitting unit isdescribed as an example. FIG. 5A is a schematic top view of a passivematrix light-emitting unit 300 described in this structure example andFIG. 5B is a schematic cross-sectional view taken along line A-A′ inFIG. 5A.

In a passive matrix (also called simple matrix) light-emitting unit, aplurality of anodes arranged in stripes (in stripe form) is provided tobe perpendicular to a plurality of cathodes arranged in stripes, and alight-emitting layer is provided therebetween at each intersection.Therefore, a pixel at an intersection of an anode selected (to which avoltage is applied) and a cathode selected emits light.

The light-emitting unit 300 in FIG. 5A is formed over a substrate 301and includes EL layers 305 between scan lines 303 and data lines 307.Partitions 309 are each provided between adjacent data lines 307 toelectrically isolate the adjacent data lines 307. A region (region 315)where one of the scan lines 303 intersects with one of the data lines307 corresponds to one pixel.

The scan lines 303 are electrically connected to a flexible printedcircuit (FPC) 311 a through an input terminal 313 a. The data lines 307are electrically connected to an FPC 311 b through a connection wiring312 and an input terminal 313 b. An input signal from the outside isinput to each of the FPC 311 a and the FPC 311 b.

A base layer 302 is formed over the substrate 301. The base layer 302 isprovided for preventing diffusion of an impurity from the substrate 301to the EL layers 305. The base layer 302 is not necessarily formed.

Over the base layer 302, the plurality of scan lines 303 is arranged instripes at regular intervals. Each of the scan lines 303 serves as alower electrode of an EL element. The connection wiring 312 may beformed using the same film as the scan lines 303.

An insulating layer 308 having opening portions corresponding torespective pixels is formed over the scan lines 303. The insulatinglayer 308 has an insulating property, and can be formed using aphotosensitive or non-photosensitive organic material such as polyimide,polyamide, polyamide imide, or acrylic, or an SOG film formed usingSiO_(x) containing an alkyl group or the like. An end portion of theinsulating layer 308 is preferably gently tapered. Note that eachopening portion corresponding to a pixel is a light-emitting region.

The plurality of partitions 309 intersecting with the scan lines 303 isprovided over the insulating layer 308. The partitions 309 are formed inparallel to each other, and are inversely tapered or T-shaped.Accordingly, the partitions 309 can physically isolate a film formedthereover.

The EL layers 305 and the data lines 307 are stacked in this order overthe scan lines 303 and the partitions 309. Each of the data lines 307serves as an upper electrode of the EL element. The EL layers 305 andthe data lines 307 are each physically isolated by the partitions 309;thus, the EL layers 305 are electrically isolated from each other andthe data lines 307 are electrically isolated from each other. Therefore,light-emitting regions corresponding to respective pixels areelectrically isolated from each other and can independently emit light.

The data lines 307 electrically isolated by the partitions 309 arewirings extending in the direction intersecting with the scan lines 303and arranged in stripes. Although films of the EL layers 305 and thedata lines 307 are formed over the partitions 309, they are physicallyand electrically isolated from the EL layers 305 and the data lines 307.

The method for manufacturing a sealed body, which is described in theabove embodiments, can be used for the light-emitting unit 300. Thelight-emitting unit 300 is placed in a highly airtight sealed regionhaving high airtightness, which is sealed with glass frit, wherebydeterioration of the EL element can be greatly suppressed. Thus, ahighly reliable light-emitting device can be provided.

Note that although FIGS. 5A and 5B illustrate an example in which adriver circuit is not provided over the substrate, an IC chip includinga driver circuit may be mounted on the substrate.

When the IC chip is mounted, a data line side IC and a scanning lineside IC, in each of which the driver circuit for transmitting a signalto a pixel portion is formed, are mounted on the periphery of (outside)the pixel portion. As a method for mounting an IC chip, a COG method,TCP, a wire bonding method, or the like can be used. The TCP is a TABtape mounted with the IC, and the TAB tape is connected to a wiring overan element formation substrate to mount the IC. The data line side ICand the scanning line side IC may be formed using a silicon substrate, asilicon on insulator (SOI) substrate, a glass substrate, a quartzsubstrate, or a plastic substrate.

Structure Example 2

In this structure example, an example of a structure in which thesealing method with glass frit according to an embodiment of the presentinvention is used for an active matrix light-emitting unit will bedescribed. FIG. 6A is a schematic top view of a light-emitting device350 in which an active matrix light-emitting unit of this example isincluded, and FIG. 6B is a schematic cross-sectional view taken alongline B-B′ in FIG. 6A.

The active matrix light-emitting device 350 of this embodiment includesa pixel portion 352 provided over a second substrate 351, a drivercircuit portion (source driver circuit) 353, and a driver circuitportion (gate driver circuit) 354. The pixel portion 352, the drivercircuit portion 353, and the driver circuit portion 354 are sealed in aglass sealed body which is surrounded by glass frit 359, the secondsubstrate 351, and a first substrate 361.

A lead wiring 355 for connecting an external input terminal whichtransmits a signal (e.g., a video signal, a clock signal, a startsignal, or a reset signal) or potential from the outside to the drivercircuit portion 353 and the driver circuit portion 354 is provided overthe second substrate 351. Here, an example is described in which an FPC356 is provided as the external input terminal. Note that although onlyan FPC is illustrated here, a printed wiring board (PWB) may be attachedto the FPC. In this specification, the light-emitting device includes inits category the light-emitting device itself and a light-emittingdevice on which an FPC or a PWB is mounted.

Next, a cross-sectional structure of the light-emitting device 350including the active matrix light-emitting unit is described withreference to FIG. 6B. Although the driver circuit portion 353, thedriver circuit portion 354, and the pixel portion 352 are formed overthe second substrate 351, the pixel portion 352 and the driver circuitportion 353 which is the source driver circuit are illustrated in FIG.6B.

In the driver circuit portion 353, an example including a CMOS circuitwhich is a combination of an n-channel TFT 371 and a p-channel TFT 372is illustrated. Note that a circuit included in the driver circuitportion can be formed using various types of circuits such as a CMOScircuit, a PMOS circuit, or an NMOS circuit. In this embodiment, adriver-integrated type in which a driver circuit and the pixel portionare formed over the same substrate is described; however, the presentinvention is not limited to this structure, and a driver circuit can beformed over a substrate that is different from the substrate over whicha pixel portion is formed.

The pixel portion 352 has a plurality of pixels each of which includes aswitching TFT 373, a current control TFT 374, and a lower electrode 375electrically connected to a wiring (a source electrode or a drainelectrode) of the current control TFT 374. An insulating layer 378 isformed so as to cover an end portion of the lower electrode 375. In thisembodiment, the insulating layer 378 is formed using a positivephotosensitive acrylic resin. Note that there is no particularlimitation on structures of the TFTs such as the switching ITT 373 andthe current control TFT 374. For example, a staggered TFT or an invertedstaggered TFT may be used. A top-gate TFT or a bottom-gate TFT may alsobe used. There is no particular limitation also on materials of asemiconductor used for the TFTs, and silicon or an oxide semiconductorsuch as an oxide including at least one of indium, gallium, and zinc maybe used. In addition, crystallinity of a semiconductor used for the TFTsis not particularly limited either; an amorphous semiconductor or acrystalline semiconductor may be used.

A light-emitting element 379 includes the lower electrode 375, an ELlayer 376, and an upper electrode 377. A structure, materials, and thelike of the light-emitting element will be described in detail inEmbodiment 4. Although not illustrated, the upper electrode 377 iselectrically connected to the FPC 356 which is an external inputterminal.

The insulating layer 378 is formed so as to cover an end portion of thelower electrode 375. In addition, in order that the upper electrode 377that is formed over the insulating layer 378 at least favorably coversthe insulating layer 378, the insulating layer 378 is preferably formedso as to have a curved surface with curvature at an upper end portion ora lower end portion. For example, it is preferable that the upper endportion or the lower end portion of the insulating layer 378 have acurved surface with a radius of curvature (0.2 μm to 3 μm). Theinsulating layer 378 can be formed using an organic compound such as anegative photosensitive resin which becomes insoluble in an etchant bylight or a positive photosensitive resin which becomes soluble in anetchant by light, or an inorganic compound such as silicon oxide orsilicon oxynitride.

A color filter 381 is provided for the first substrate 361 in a positionoverlapping with the light-emitting element 379. Any of the materialsand structures described in the above embodiments can be applied to thecolor filter 381. A black matrix 382 is provided in a region which doesnot overlap with the light-emitting element 379. When an end portion ofthe color filter 381 overlaps with the black matrix 382, light leakagecan be suppressed. A material which does not transmit light emitted fromthe light-emitting element 379 can be used for the black matrix 382, anda material such as metal or an organic resin can be used. Alternatively,the black matrix 382 may be formed using the same layer as a heatgeneration layer 358.

An overcoat 383 covering the color filter 381 and the black matrix 382is formed. The overcoat 383 is formed using a material which transmitslight emitted from the light-emitting element 379, and an insulatingfilm including silicon or an organic insulating film can be used, forexample. Note that the overcoat 383 is not necessarily formed.

Although only one light-emitting element 379 is illustrated in thecross-sectional view of FIG. 6B, a plurality of light-emitting elementsis arranged in matrix in the pixel portion 352. For example,light-emitting elements that emit light of three kinds of colors (R, G,and B) are selectively formed in the pixel portion 352, so that alight-emitting device capable of full color display can be obtained.Moreover, a light-emitting device capable of full color display can beobtained by a combination of a color filter and a light-emitting elementincluding an EL layer emitting white light to be described in a laterembodiment. The light-emitting element can have either a top emissionstructure or a dual emission structure.

The light-emitting element 379 is provided in a sealed region surroundedby the first substrate 361, the second substrate 351, and the glass frit359. The sealed region may be filled with a rare gas, a nitrogen gas, ora solid, or may be a reduced-pressure atmosphere.

For the first substrate 361, the heat generation layer 358 is providedin a region overlapping with the glass frit 359. In the case where theglass frit 359 includes a conductive material, the heat generation layer358 is not necessarily provided. In the case where the glass frit 359includes a conductive material, an insulating layer is provided over thelead wiring 355 for the prevention of short circuit between the leadwiring 355 and the glass frit 359. A film which has favorable adhesionto the glass frit 359 and can withstand temperature at which the glassfrit 359 is melted is used as the insulating layer. For example, anoxide film or a nitride film such as a silicon oxide film, a siliconnitride film, or an aluminum oxide film can be used.

As described above, a light-emitting device including an active matrixlight-emitting unit formed using the method for manufacturing a sealedbody according to an embodiment of the present invention can beobtained. The light-emitting device has a longer lifetime and is strongagainst external force such as impact, distortion, or the like.

Embodiment 4

In this embodiment, examples of EL layers that can be applied to anembodiment of the present invention will be described with reference toFIGS. 7A to 7C.

As illustrated in FIG. 7A, an EL layer 105 is provided between a firstelectrode 103 and a second electrode 107. The first electrode 103 andthe second electrode 107 can have a structure similar to that of thelower electrode or the upper electrode, which are described in any ofthe above embodiments.

A light-emitting element including the EL layer 105 described as anexample in this embodiment can be used in any of the light-emittingdevices described as examples in the above embodiments.

The EL layer 105 includes at least a light-emitting layer containing alight-emitting organic compound. In addition, the EL layer 105 can havea stacked-layer structure in which a layer containing a substance havinga high electron-transport property, a layer containing a substancehaving a high hole-transport property, a layer containing a substancehaving a high electron-injection property, a layer containing asubstance having a high hole-injection property, a layer containing abipolar substance (a substance having a high electron-transport propertyand a high hole-transport property), and the like are combined asappropriate. In this embodiment, in the EL layer 105, a hole-injectionlayer 701, a hole-transport layer 702, a layer 703 containing alight-emitting organic compound, an electron-transport layer 704, and anelectron-injection layer 705 are stacked in this order from the firstelectrode 103 side. Note that the stacking order may be inversed.

A manufacturing method of the light-emitting element illustrated in FIG.7A will be described.

The hole-injection layer 701 is a layer containing a substance having ahigh hole-injection property. As the substance having a highhole-injection property, for example, a metal oxide such as molybdenumoxide, titanium oxide, vanadium oxide, rhenium oxide, ruthenium oxide,chromium oxide, zirconium oxide, hafnium oxide, tantalum oxide, silveroxide, tungsten oxide, or manganese oxide can be used. Aphthalocyanine-based compound such as phthalocyanine (abbreviation:H₂Pc), or copper(II) phthalocyanine (abbreviation: CuPc) can also beused.

Alternatively, an aromatic amine compound, which is a low molecularorganic compound or the like, can be used.

Any of high molecular compounds (e.g., oligomers, dendrimers, orpolymers) can also be used. A high molecular compound to which acid isadded can be used.

In particular, for the hole-injection layer 701, a composite material inwhich an acceptor substance is mixed with an organic compound having ahigh hole-transport property is preferably used. With the use of thecomposite material in which an acceptor substance is added to asubstance having a high hole-transport property, excellent holeinjection from the first electrode 103 can be obtained, which results ina reduction in the drive voltage of the light-emitting element. Such acomposite material can be formed by co-evaporation of a substance havinga high hole-transport property and an acceptor substance. When thehole-injection layer 701 is formed using the composite material, holesare easily injected from the first electrode 103 into the EL layer 105.

As the organic compound used for the composite material, any of avariety of compounds such as aromatic amine compounds, carbazolederivatives, aromatic hydrocarbons, and high molecular compounds (e.g.,oligomers, dendrimers, and polymers) can be used. The organic compoundused for the composite material is preferably an organic compound havinga high hole-transport property. Specifically, a substance having a holemobility of 10⁻⁶ cm²/Vs or higher is preferably used. Note that anyother substances may also be used as long as the hole-transport propertythereof is higher than the electron-transport property thereof.

As the organic compound which can be used for the composite material, anaromatic amine compound, a carbazole derivative, an aromatic hydrocarboncompound having a high hole mobility can be used.

Examples of the acceptor substance include organic compounds andtransition metal oxides. In addition, oxides of metals belonging toGroups 4 to 8 in the periodic table can be also given. Specifically,vanadium oxide, niobium oxide, tantalum oxide, chromium oxide,molybdenum oxide, tungsten oxide, manganese oxide, and rhenium oxide arepreferable because of their electron-accepting properties. Among these,molybdenum oxide is particularly preferable because it is stable in theair, has a low hygroscopic property, and is easily handled.

The composite material may be formed using the above electron acceptorand the above high molecular compound and used for the hole-injectionlayer 701.

The hole-transport layer 702 is a layer containing a substance having ahigh hole-transport property. As the substance having a highhole-transport property, for example, an aromatic amine compound can beused. The substance has a hole mobility of 10⁻⁶ cm²/Vs or higher. Notethat any other substances may also be used as long as the hole-transportproperty thereof is higher than the electron-transport property thereof.Note that the layer containing a substance having a high hole-transportproperty is not limited to a single layer and may be a stack of two ormore layers containing any of the above substances.

In addition, a carbazole derivative, an anthracene derivative, or a highmolecular compound having a high hole-transport property may also beused for the hole-transport layer 702.

For the layer 703 containing a light-emitting organic compound, afluorescent compound which exhibits fluorescence or a phosphorescentcompound which exhibits phosphorescence can be used.

Note that the layer 703 containing a light-emitting organic compound mayhave a structure in which a light-emitting organic compound (guestmaterial) is dispersed in another substance (host material). As a hostmaterial, a variety of kinds of materials can be used, and it ispreferable to use a substance which has a higher lowest unoccupiedmolecular orbital level (LUMO level) than the light-emitting materialand has a lower highest occupied molecular orbital level (HOMO level)than the light-emitting material.

Alternatively, as the host material, plural kinds of materials can beused. For example, in order to suppress crystallization, a substancewhich suppresses crystallization may be further added. In addition, adifferent kind of substance may be further added in order to efficientlytransfer energy to the guest material.

When a structure in which a guest material is dispersed in a hostmaterial is employed, crystallization of the layer 703 containing alight-emitting organic compound can be suppressed. Further,concentration quenching due to high concentration of the guest materialcan be suppressed.

A high molecular compound can also be used for the layer 703 containinga light-emitting organic compound.

Further, by providing a plurality of layers each containing alight-emitting organic compound and making the emission colors of thelayers different, light emission having a desired color can be obtainedfrom the light-emitting element as a whole. For example, in alight-emitting element including two layers each containing alight-emitting organic compound, the emission color of a first layercontaining a light-emitting organic compound and the emission color of asecond layer containing a light-emitting organic compound are madecomplementary, so that the light-emitting element as a whole can emitwhite light. Note that “complementary colors” refer to colors that canproduce an achromatic color when mixed. In other words, when lightsobtained from substances which emit light of complementary colors aremixed, white emission can be obtained. This can be applied to alight-emitting element including three or more layers each containing alight-emitting organic compound.

The electron-transport layer 704 is a layer containing a substancehaving a high electron-transport property. Examples of the substancehaving a high electron-transport property are mainly ones that have anelectron mobility of 10⁻⁶ cm²/Vs or higher. The electron-transport layeris not limited to a single layer, and two or more layers made of theaforementioned substance may be stacked.

The electron-injection layer 705 is a layer containing a substancehaving a high electron-injection property. For the electron-injectionlayer 705, an alkali metal, an alkaline earth metal, or a compoundthereof, such as lithium, cesium, calcium, lithium fluoride, cesiumfluoride, calcium fluoride, or lithium oxide, can be used. A rare earthmetal compound such as erbium fluoride can also be used. Any of theabove substances for forming the electron-transport layer 704 can alsobe used.

Note that the hole-injection layer 701, the hole-transport layer 702,the layer 703 containing a light-emitting organic compound, theelectron-transport layer 704, and the electron-injection layer 705 whichare described above can each be formed by a method such as anevaporation method (e.g., a vacuum evaporation method), an inkjetmethod, or a coating method.

As illustrated in FIG. 7B, a plurality of EL layers may be stackedbetween the first electrode 103 and the second electrode 107. In thatcase, a charge generation layer 803 is preferably provided between afirst EL layer 800 and a second EL layer 801 which are stacked. Thecharge generation layer 803 can be formed using the above compositematerial. Further, the charge generation layer 803 may have astacked-layer structure including a layer containing the compositematerial and a layer containing another material. In that case, as thelayer containing another material, a layer containing anelectron-donating substance (donor substrate) and a substance having ahigh electron-transport property, a layer formed of a transparentconductive film, or the like can be used. As for a light-emittingelement having such a structure, problems such as energy transfer andquenching hardly occur, and a light-emitting element which has both highemission efficiency and long lifetime can be easily obtained due toexpansion in the choice of materials. Moreover, a light-emitting elementwhich provides phosphorescence from one EL layer and fluorescence fromanother EL layer can be easily obtained. Note that this structure can becombined with any of the above structures of the EL layer.

Further, by forming EL layers to emit light of different colors fromeach other, a light-emitting element as a whole can provide lightemission of a desired color. For example, in a light-emitting elementhaving the two EL layers, the emission colors of the first and second ELlayers are complementary, so that the light-emitting element can be madeto emit white light as a whole. Note that “complementary colors” referto colors that can produce an achromatic color when mixed. In otherwords, when lights obtained from substances which emit light ofcomplementary colors are mixed, white emission can be obtained. This canbe applied to a light-emitting element having three or more EL layers.

In order to obtain white light with favorable color renderingproperties, light whose emission spectrum covers the whole visible lightrange is needed and thus a light-emitting element in which three or moreEL layers are stacked is preferably used. For example, such alight-emitting element can be formed by stacking EL layers emittinglight of the respective colors of red, blue, and green. In this manner,the color rendering properties of a light-emitting element can beimproved by stacking EL layers of different three or more colors.

An optical adjustment layer may be formed between the first electrode103 and the second electrode 107. The optical adjustment layer is alayer for adjusting the optical distance between a reflective electrodeand a light-transmitting electrode. With the optical adjustment layer,light with a wavelength in a specific range can be enhanced and thus thecolor tone can be adjusted.

As illustrated in FIG. 7C, the EL layer 105 may include, between thefirst electrode 103 and the second electrode 107, the hole-injectionlayer 701, the hole-transport layer 702, the layer 703 containing alight-emitting organic compound, the electron-transport layer 704, anelectron-injection buffer layer 706, an electron-relay layer 707, and acomposite material layer 708 which is in contact with the secondelectrode 107.

The composite material layer 708 which is in contact with the secondelectrode 107 is preferably provided, in which case damage caused to theEL layer 105 particularly when the second electrode 107 is formed by asputtering method can be reduced. The composite material layer 708 canbe formed using the above composite material in which an acceptorsubstance is mixed with an organic compound having a high hole-transportproperty.

Further, by providing the electron-injection buffer layer 706, aninjection barrier between the composite material layer 708 and theelectron-transport layer 704 can be reduced; thus, electrons generatedin the composite material layer 708 can be easily injected to theelectron-transport layer 704.

A substance having a high electron-injection property can be used forthe election-injection buffer layer 706: for example, an alkali metal,an alkaline earth metal, a rare earth metal, a compound of the abovemetal (e.g., an alkali metal compound (including an oxide such aslithium oxide, a halide, or a carbonate such as lithium carbonate orcesium carbonate), an alkaline earth metal compound (including an oxide,a halide, or a carbonate), or a rare earth metal compound (including anoxide, a halide, or a carbonate)).

Further, in the case where the electron-injection buffer layer 706contains a substance having a high electron-transport property and adonor substance, the donor substance is preferably added so that themass ratio of the donor substance to the substance having a highelectron-transport property is from 0.001:1 to 0.1:1. Note that as thedonor substance, an organic compound such as tetrathianaphthacene(abbreviation: TTN), nickelocene, or decamethylnickelocene can be usedas well as an alkali metal, an alkaline earth metal, a rare earth metal,and a compound of the above metal (e.g., an alkali metal compound(including an oxide of lithium oxide or the like, a halide, and acarbonate such as lithium carbonate or cesium carbonate), an alkalineearth metal compound (including an oxide, a halide, and a carbonate),and a rare earth metal compound (including an oxide, a halide, and acarbonate)). Note that a material similar- to the material for theelectron transport layer 704 described above can be used as thesubstance having a high electron-injection property.

Furthermore, the electron-relay layer 707 is preferably formed betweenthe electron-injection buffer layer 706 and the composite material layer708. The electron-relay layer 707 is not necessarily provided; however,by providing the electron-relay layer 707 having a highelectron-transport property, electrons can be rapidly transported to theelectron-injection buffer layer 706.

The structure in which the electron-relay layer 707 is sandwichedbetween the composite material layer 708 and the electron-injectionbuffer layer 706 is a structure in which the acceptor substancecontained in the composite material layer 708 and the donor substancecontained in the electron-injection buffer layer 706 are less likely tointeract with each other; thus, their functions hardly interfere witheach other. Thus, an increase in the driving voltage can be prevented.

The electron-relay layer 707 contains a substance having a highelectron-transport property and is found so that the LUMO level of thesubstance having a high electron-transport property is located betweenthe LUMO level of the acceptor substance contained in the compositematerial layer 708 and the LUMO level of the substance having a highelectron-transport property contained in the electron-transport layer704. In the case where the electron-relay layer 707 contains a donorsubstance, the donor level of the donor substance is controlled so as tobe located between the LUMO level of the acceptor substance in thecomposite material layer 708 and the LUMO level of the substance havinga high electron-transport property contained in the electron-transportlayer 704. As a specific value of the energy level, the LUMO level ofthe substance having a high electron-transport property contained in theelectron-relay layer 707 is preferably greater than or equal to −5.0 eV,more preferably greater than or equal to −5.0 eV and less than or equalto −3.0 eV.

As the substance having a high electron-transport property contained inthe electron-relay layer 707, a phthalocyanine-based material or a metalcomplex having a metal-oxygen bond and an aromatic ligand is preferablyused.

As the metal complex having a metal-oxygen bond and an aromatic ligand,which is contained in the electron-relay layer 707, a metal complexhaving a metal-oxygen double bond is preferably used. The metal-oxygendouble bond has an acceptor property (a property of easily acceptingelectrons); thus, electrons can be transferred (donated and accepted)more easily. Further, the metal complex having a metal-oxygen doublebond is considered stable. Thus, the use of the metal complex having ametal-oxygen double bond makes it possible to drive the light-emittingelement at low voltage more stably.

As a metal complex having a metal-oxygen bond and an aromatic ligand, aphthalocyanine-based material is preferable. In particular, a substancein which a metal-oxygen double bond is more likely to act on anothermolecular in terms of a molecular structure and which has a highacceptor property is preferably used.

Note that a phthalocyanine-based material having a phenoxy group ispreferable as the phthalocyanine-based material described above.Specifically, a phthalocyanine derivative having a phenoxy group, suchas PhO-VOPc, is preferable. A phthalocyanine derivative having a phenoxygroup is soluble in a solvent, and thus has an advantage of being easilyhandled during formation of a light-emitting element and an advantage offacilitating maintenance of an apparatus used for film formation.

The electron-relay layer 707 may further contain a donor substance.Examples of the donor substance include an organic compound such astetrathianaphthacene (abbreviation: TTN), nickelocene, anddecamethylnickelocene, in addition to an alkali metal, an alkaline earthmetal, a rare earth metal, and a compound of the above metals (e.g., analkali metal compound (including an oxide such as lithium oxide, ahalide, and a carbonate such as lithium carbonate or cesium carbonate),an alkaline earth metal compound (including an oxide, a halide, and acarbonate), and a rare earth metal compound (including an oxide, ahalide, and a carbonate)). When such a donor substance is contained inthe electron-relay layer 707, electrons can be transferred easily andthe light-emitting element can be driven at lower voltage.

In the case where a donor substance is contained in the electron-relaylayer 707, in addition to the materials described above as the substancehaving a high electron-transport property, a substance having a LUMOlevel greater than the acceptor level of the acceptor substancecontained in the composite material layer 708 can be used. As a specificenergy level, a LUMO level is greater than or equal to −5.0 eV,preferably greater than or equal to −5.0 eV and less than or equal to−3.0 eV. As examples of such a substance, a perylene derivative and anitrogen-containing condensed aromatic compound can be given. Note thata nitrogen-containing condensed aromatic compound is preferably used forthe electron-relay layer 707 because of its stability.

Note that in the case where a donor substance is contained in theelectron-relay layer 707, the electron-relay layer 707 may be formed bya method such as co-evaporation of the substance having a highelectron-transport property and the donor substance.

The hole-injection layer 701, the hole-transport layer 702, the layer703 containing a light-emitting organic compound, and theelectron-transport layer 704 may each be formed using any of thematerials given above.

As described above, the EL layer 105 of this embodiment can be formed.

This embodiment can be combined with any of the other embodimentsdisclosed in this specification as appropriate.

Embodiment 5

In this embodiment, an example of an electronic device or a lightingdevice including a light-emitting device formed using the method formanufacturing a sealed body according to an embodiment of the presentinvention will be described with reference to FIGS. 8A to 8E.

Examples of the electronic devices to which the light-emitting device isapplied are television devices (also referred to as TV or televisionreceivers), monitors for computers and the like, cameras such as digitalcameras and digital video cameras, digital photo frames, mobile phones(also referred to as cellular phones or cellular phone devices),portable game machines, portable information terminals, audio playbackdevices, large game machines such as pachinko machines, and the like.Specific examples of these electronic devices are illustrated in FIGS.8A to 8E.

FIG. 8A illustrates an example of a television device. In the televisiondevice 7100, a display portion 7103 is incorporated in a housing 7101.The display portion 7103 is capable of displaying images, and thelight-emitting device can be used for the display portion 7103. Inaddition, here, the housing 7101 is supported by a stand 7105.

The television device 7100 can be operated by an operation switch of thehousing 7101 or a separate remote controller 7110. With operation keys7109 of the remote controller 7110, channels and volume can becontrolled and images displayed on the display portion 7103 can becontrolled. Furthermore, the remote controller 7110 may be provided witha display portion 7107 for displaying data output from the remotecontroller 7110.

Note that the television device 7100 is provided with a receiver, amodem, and the like. With the receiver, a general television broadcastcan be received. Furthermore, when the television device 7100 isconnected to a communication network by wired or wireless connection viathe modem, one-way (from a transmitter to a receiver) or two-way(between a transmitter and a receiver, between receivers, or the like)data communication can be performed.

FIG. 8B illustrates a computer, which includes a main body 7201, ahousing 7202, a display portion 7203, a keyboard 7204, an externalconnecting port 7205, a pointing device 7206, and the like. Note thatthis computer is manufactured using the light-emitting device for thedisplay portion 7203.

FIG. 8C illustrates a portable game machine, which includes twohousings, a housing 7301 and a housing 7302, which are connected with ajoint portion 7303 so that the portable game machine can be opened orfolded. A display portion 7304 is incorporated in the housing 7301 and adisplay portion 7305 is incorporated in the housing 7302. In addition,the portable game machine illustrated in FIG. 8C includes a speakerportion 7306, a recording medium insertion portion 7307, an LED lamp7308, input means (an operation key 7309, a connection terminal 7310, asensor 7311 (a sensor having a function of measuring force,displacement, position, speed, acceleration, angular velocity,rotational frequency, distance, light, liquid, magnetism, temperature,chemical substance, sound, time, hardness, electric field, current,voltage, electric power, radiation, flow rate, humidity, gradient,oscillation, odor, or infrared rays), and a microphone 7312), and thelike. Needless to say, the structure of the portable game machine is notlimited to the above as long as a light-emitting device can be used forat least either the display portion 7304 or the display portion 7305, orboth, and may include other accessories as appropriate. The portablegame machine illustrated in FIG. 8C has a function of reading out aprogram or data stored in a storage medium to display it on the displayportion, and a function of sharing information with another portablegame machine by wireless communication. The portable game machine inFIG. 8C can have a variety of functions without limitation to the abovefunctions.

FIG. 8D illustrates an example of a mobile phone. A mobile phone 7400 isprovided with a display portion 7402 incorporated in a housing 7401,operation buttons 7403, an external connection port 7404, a speaker7405, a microphone 7406, and the like. Note that the mobile phone 7400is manufactured using the light-emitting device for the display portion7402.

When the display portion 7402 of the mobile phone 7400 illustrated inFIG. 8D is touched with a finger or the like, data can be input into themobile phone 7400. Further, operations such as making a call andcreating e-mail can be performed by touch on the display portion 7402with a finger or the like.

There are mainly three screen modes of the display portion 7402. Thefirst mode is a display mode mainly for displaying images. The secondmode is an input mode mainly for inputting data such as text. The thirdmode is a display-and-input mode in which two modes of the display modeand the input mode are combined:

For example, in the case of making a call or composing an e-mail, a textinput mode mainly for inputting text is selected for the display portion7402 so that text displayed on a screen can be input. In this case, itis preferable to display a keyboard or number buttons on almost theentire screen of the display portion 7402.

When a detection device including a sensor for detecting inclination,such as a gyroscope or an acceleration sensor, is provided inside themobile phone 7400, display on the screen of the display portion 7402 canbe automatically changed by determining the orientation of the mobilephone 7400 (whether the mobile phone is placed horizontally orvertically for a landscape mode or a portrait mode).

The screen modes are switched by touching the display portion 7402 oroperating the operation buttons 7403 of the housing 7401. The screenmodes can also be switched depending on kinds of images displayed on thedisplay portion 7402. For example, when a signal of an image displayedon the display portion is a signal of moving image, data, the screenmode is switched to the display mode. When the signal is a signal oftext data, the screen mode is switched to the input mode.

Moreover, in the input mode, when input by touching the display portion7402 is not performed within a specified period while a signal detectedby an optical sensor in the display portion 7402 is detected, the screenmode may be controlled so as to be switched from the input mode to thedisplay mode.

The display portion 7402 may function as an image sensor. For example,an image of a palm print, a fingerprint, or the like is taken by touchon the display portion 7402 with the palm or the finger, wherebypersonal authentication can be performed. Further, by providing abacklight or a sensing light source which emits a near-infrared light inthe display portion, an image of a finger vein, a palm vein, or the likecan be taken.

FIG. 8E illustrates an example of a lighting device. In a lightingdevice 7500, light-emitting devices 7503 a to 7503 d of an embodiment ofthe present invention are incorporated in a housing 7501 as lightsources. The lighting device 7500 can be attached to a ceiling, a wall,or the like.

The light-emitting device according to an embodiment of the presentinvention includes a light-emitting panel which can be formed in a filmform. Thus, when the light-emitting device is attached to a base with acurved surface, the light-emitting device with a curved surface can beobtained. In addition, when the light-emitting device is located in ahousing with a curved surface, an electronic device or a lighting devicewith a curved surface can be obtained.

Further, the light-emitting device includes a light-emitting panel whichemits light having high brightness and a pale color and causing lesseyestrain even in the case of long-time use, light of a bright redcolor, and light of a bright color different from the other colors. Byadjusting conditions under which the light-emitting element is drivenfor each emission color, a lighting device whose hue can be adjusted bya user can be achieved.

The method for manufacturing a sealed body with the use of glass fritaccording to an embodiment of the present invention is used for thelight-emitting device used for the electronic device or the lightingdevice. Thus, a highly reliable electronic device or lighting device canbe obtained because the light-emitting element can be enclosed in thesealed region having high airtightness.

This embodiment can be combined with any of the other embodimentsdisclosed in this specification as appropriate.

This application is based on Japanese Patent Application serial no.2011-133957 filed with Japan Patent Office on Jun. 16, 2011, the entirecontents of which are hereby incorporated by reference.

1-15. (canceled)
 16. A sealed body comprising: a first substrate; asecond substrate; and a glass frit comprising a conductive material,wherein a closed space surrounded by the first substrate, the secondsubstrate, and the glass frit is formed.
 17. The sealed body accordingto claim 16, wherein the conductive material comprises any one of iron,tungsten, and molybdenum.
 18. The sealed body according to claim 16,wherein the conductive material is a powder material.
 19. The sealedbody according to claim 18, wherein a diameter of the powder material islarger than or equal to 1 nm and smaller than or equal to 100 μm. 20.The sealed body according to claim 16, the glass frit further comprisinga binder and a frit material.
 21. The sealed body according to claim 20,wherein the frit material comprises one or more compounds selected frommagnesium oxide, calcium oxide, barium oxide, lithium oxide, sodiumoxide, potassium oxide, boron oxide, vanadium oxide, zinc oxide,tellurium oxide, aluminum oxide, silicon dioxide, lead oxide, tin oxide,phosphorus oxide, ruthenium oxide, rhodium oxide, iron oxide, copperoxide, titanium oxide, tungsten oxide, bismuth oxide, and antimonyoxide.
 22. A light-emitting device comprising the sealed body accordingto claim 16, wherein the second substrate is provided with alight-emitting unit.
 23. The light-emitting device according to claim22, the light-emitting unit comprising an EL element, the EL elementcomprising: an anode; a cathode; and an EL layer between the anode andthe cathode, wherein the EL layer comprises a light-emitting layer. 24.The light-emitting device according to claim 22, wherein the firstsubstrate is provided with a color filter.
 25. A lighting devicecomprising the light-emitting device according to claim
 22. 26. Adisplay device comprising the light-emitting device according to claim22.